Conventional forming of sheet metal, particularly when blanking out openings, and forming shapes or formations around the openings, has for many years been carried out using upper and lower dies in what is essentially a stationary press. The sheet metal is placed between the two dies, the dies close and open and the metal is formed. Major improvements have been made in this process, by rotary forming systems. In these systems the sheet metal is fed from a roll and moves continuously between a pair of upper and lower rolls. On these rolls there are pairs of dies. As the rolls rotate, the pairs of dies meet, close and open, and form the sheet metal. These systems in theory have major advantages over stationary press operations. The sheet metal can be fed continuously, in some cases at considerable line speeds in excess of 200 feet per minute or more. The sheet metal once formed can be cut off into suitable work pieces, and the entire operation can be carried out automatically at high speed. In fact, however it has been found that there are numerous problems in these proposals. Rotary machines of this type have been proposed for many years. Some such machines have had a limited degree of success. In particular, if all that is required is to form a series of depressions or shapes in the sheet metal, such rotary machines may be relatively satisfactory. However, when it is desired to blank out openings in the sheet metal and then form shapes or bends around the sheet metal at the edges of the openings the problems become much more complex. The problems are further compounded by the fact that one of the major uses for such a sheet metal product, if it could be produced satisfactorily, would be as a replacement for wooden studs used in construction. Such metal studs must necessarily be formed with lengthwise bends or shapes, so that they may carry loads. Sheet metal studs of this type with a simple c-section have been made for many years, since at least the 1930's. However, such sheet metal studs also have disadvantages in that they act as efficient pathways for the transfer of heat. As a result, buildings made with such sheet metal studs suffer from considerable heat losses, greatly in excess of that experienced with wooden studs. To overcome this problem, various proposals have been made for forming openings in the sheet metal studs. One such form of proposal is shown in U.S. Pat. No. 2,088,781. Another proposal is shown in Canadian Patent 1192015. In both of these proposals, and many other patents of similar design, the design is based on a sheet metal stud having angled formations along either side edge which are continuous, and having a series of generally triangular or trapezoidal openings formed in the web between the edges. The triangular openings are alternately reversed in direction, so as to produce struts extending between the two edges of the stud which effectively form a zigzag up the length of the stud. The forming of the longitudinal edge formations is relatively easy to carry out using conventional roll forming dies of a type which are well in the art and require no description. However the forming of the openings, using rotary machines presents a series of complex problems. The openings must be formed by pairs of dies which alternate from one pair of dies to the other in the orientation of the opening. In addition, around each of the openings there are formed flanges to increase the strength of the stud and to increase the strength of the diagonal zigzag struts. One of the problems in designing such machines is that the dies are travelling around a circular path. The sheet metal is travelling on a linear path. The dies will contact the sheet metal just before the dies close and will remain in contact with the sheet metal until just after the dies open. The dies travel along an arcuate path. During this brief time span, there is a slight change in linear speed between the linear speed of the dies themselves and the linear speed of the metal. Just prior to closing and just after opening, the dies will be moving at a slightly slower linear speed than the sheet metal, and only when fully closed will the dies be moving momentarily at the same speed as the sheet metal. While this may not seem a significant factor, it causes distortion of the sheet metal especially when the line speeds are increased. Another problem is in controlling the orientations of the pairs of dies prior to closing and just after opening. It is apparent that the dies, which are similar to dies used in stationary stamping presses, must lie in predetermined planes in order to form the work piece. In a rotary apparatus the planes of each of the dies in any one pair must be brought parallel to one another just prior to closing on the sheet metal and must remain parallel through closing and after opening, for a certain length of time. In order to achieve this the dies themselves are mounted on die carriers. The die carriers are mounted on semi rotary bearings. These semi rotary bearings are carried on a central rotor press shaft. The die carriers are capable of swinging relative to the central shaft. In this way, the die carriers, and their dies can be swung into the necessary parallel orientation just prior to closing, and remain in that orientation until just after opening.
The problem that exists in the design of such a rotary machine is in guiding the die carriers, so that they swing into the appropriate parallel planes and remain there during the operative arcuate part of the cycle. Various different forms of guides have been designed for use in different machines, some of which are described above in the Patents referred to. These guide rollers are cam followers, which are mounted on the semi rotary die carriers. Cam plates are secured on one or both sides of the rotor press shaft. The guide rollers rotate around the cams as the rotor shaft rotates. The cams have a predetermined profile such that they control the orientation of the semi rotary die carriers as they travel around the rotation of the rotor shaft. The location of the two guide rollers on each die carrier presents problems. The guide rollers should preferably be located with at least one on the leading edge and one on the trailing edge of the die carrier, so as to provide a sufficient degree of control for levelling the die carriers as they close and open on the sheet metal. This however in turn presents problems, since the profile of the cams on which those two guide rollers must necessarily ride, will be different from each other. The two guide rollers must necessarily follow two different guide paths as they rotate. One way of achieving this result was to provide a leading guide roller at one end of the die carrier and a trailing guide roller at the other end of the die carrier. A first cam plate was mounted adjacent to one end of the rotor shaft and a second cam plate was located adjacent the other end of the rotor shaft. A problem which had also been encountered was that when the guide rollers were designed to ride in a groove in a cam plate, it was found that with the guide roller rotating in contact with one surface of the groove, this necessarily involved the guide roller rotating in a reverse direction against the opposite surface of the groove. One solution to this problem was to enlarge the groove so as to overcome the problems of rapid wear. This resulted in a less than perfect guidance around the arc of rotation which meant that the dies were not always guided into the exactly parallel planes which were required. One proposal for a solution was the provision of guide rollers in pairs on the same axles. Even with this improvement however it has been found that with heavier die carriers and dies, and when operating at higher rotational speeds, there was still some slack in the guidance system, and portions of the guidance system were unable to provide adequate control for the die carriers. It appears from further development that guidance rollers should be provided along both the leading and the trailing edges of the die carriers, so as to permit heavier capacity dies to be used, and higher operating speeds to be achieved. However, for various reasons it has been found difficult to provide guidance by means of guide rollers on the leading edge of the die carriers, and also along the trailing edge of the die carriers, without providing some form of guide cams adjacent to each end of the central rotor shaft. The leading and trailing guide rollers must follow different patterns.
It is also desirable to provide controls for the fine adjustments of linear speed which are required in order to match the linear speeds of the die carriers with the linear speed of the sheet metal. The speed adjustments required to match the linear speeds of the die carriers with the linear speed of the sheet metal in the past have been achieved by dies and die carriers which incorporated slides and springs which simply enabled the dies themselves to speed up when they contacted the sheet metal and again as the dies opened. This form of speed control was achieved simply by the dies contacting the sheet metal and being moved against springs.
Another and entirely different set of requirements arises when it is realized that such a rotary machine will normally involve the use of shaft support plates and shaft support bearings at each end of the central rotor shaft. This in turn means that each new piece of sheet metal must be introduced between the upper and lower rotor shafts in a somewhat intricate threading operation. In many situations it has been found desirable to provide a rotary apparatus of this kind and to provide roller dies to compliment the rotary apparatus which are supported on bearings stands only at one end of each of the shafts, leaving the opposite end of each shaft unsupported. This type of “open sided” rotary apparatus has great advantages over the more conventional design, since it enables a much greater flexibility in the rearrangement of dies, and the retooling of the apparatus, and the threading of new sheet metal work pieces and the like, all of which is made much easier having the so called “open ended” rotary apparatus which is accessible from one end without the use of bearings supports previously used at both ends of each shaft.